LQWT09

LQWT Field Team 2009

The first field season of the Late Quaternary Human Evolution in West Turkana Project focused on the archaeology and human palaeontology of the area west of the Natome River, a non-permanent small tributary of the Kerio River, on the southwestern floodplains of Lake Turkana. The overall aims were to begin the reconstruction of the geomorphological history of the area in relation to the chronology of the changing levels of the lake in the past, as well as to survey for archaeological artefacts and animal and hominin fossil remains.

The work during the 2009 field season focused on a relatively small area of ca. 1 x 2 km to the west of the seasonal stream known as Natome, and ca. 4.5 km west of the Kerio, with the specific objectives of:

carrying out a focused palaeontological and archaeological survey of a small area to the west of the Natome seasonal river, where fossil remains had been identified previously;

excavating a small number of trenches at the edge of the low eroding hills that make up the landscape locally, establish stratigraphic patterns, and collect samples for environmental and chronological analysis.

View of OFB Hill, Natome 2009

The landscape of the area is ‘badlands’ – highly dissected sediments of lacustrine/fluvial nature, mostly of later Quaternary age, forming irregular and eroded, sloping hills, approximately 8-15m above the surrounding landscape. The eroded slopes of the hills often expose layers of gastropods and/or plant root casts, indicative of points in the past when the area was part of the lake beaches or marshy. The estimated maximum level of the early Holocene lake (ca. 430m above sea level) cuts through the locality. The surface of the latter is sandy/pebbly, and contains a large number of fragmented fossil bones at varying densities, as well as occasional archaeological artefacts. We have called this locality Natome, as the local Turkana call the area.

This locality became known to Richard and Meave Leakey as the place where a fossilised human skull was found. The skull was given to missionaries, from whom it was later retrieved in 2006/7; the fossil is now housed at TBI-Turkwell, and accessioned to the collections of the National Museums of Kenya as KNM WT 71180.

KNM-WT-71180,-Natome

The skull is a modern human cranium, probably of early Holocene date, originally covered to a great extent in a matrix which was encrusted gastropod shells. It has since been cleaned by Christopher Kiarie (2010). The locality was briefly visited in 2007 by Marta Mirazon Lahr and Meave Leakey, when a virtually complete human mandible was found on the surface of a hill, and again in 2008 by Marta Mirazon Lahr, Robert Foley and Kamoya Kimeu, when two partial human occipital bones, as well as a number of human postcranial fragments were again found on the surface of the hills. Some of these fragments are significantly more fossilised than the other human remains mentioned. The area was also briefly surveyed in the past by Frank Brown, who noted the presence of human remains and other mammals, and more recently by Elizabeth Hildebrand and John Shea, who similarly recorded human remains.

The survey focused on recording (through GPS and Total Station) the distribution of surface fossils and artefacts, excavating a small number of step trenches down the slope of some of the hills to obtain environmental and OSL dating samples, and collecting samples of gastropod shells from different levels for potential dating.

In terms of palaeoanthropological finds, the survey recorded several more human remains, ranging from single, isolated fragments, to two exposed very eroded and fragmentary skeletons. The level of mineralisation varies greatly, with some of the remains appearing just semi-fossilised, and others heavily mineralised, usually very dark. The archaeological material found was neither rich or in context. It consisted mainly of LSA surface finds, mostly singular, occasional bone harpoons, and at one edge of the locality, a set of pottery sherds. The fauna, in contrast, is very rich. Faunal remains consisted mainly of fish, as expected in these sediments, but also crocodiles, hippos, bovids and pigs. Much of the faunal remains showed evidence of having been trampled and broken recently, clearly linked to the ubiquitous presence of large numbers of goats.

Summary

Natome represents an exciting new locality in West Turkana because of the wealth of fossils it contains. It consists of a complex landscape eroded by winds, as well as the recurrent rising and receding waters of the lake in the past. This erosion has not only shaped the hills and exposed their slopes, but most likely removed whole sedimentary layers differentially in each case, as well as depositing new beach and lake-edge sediments in turn, creating a complex stratigraphic picture. The aeolian deflation of the hills has generated a localised surface distribution of fossils and artefacts that seem to have deflated without any significant horizontal movement (as evident by the findings of articulating bones), while water levels have probably moved some of these surface elements along (as evident, for example, in the case of the two re-fitting fragments of heavily fossilised human occipital found c. 80 m apart). Despite the numerous step trenches excavated, no fossiliferous horizons were identified from which the fossils found on the surface could be derived. This could mean that those sediments no longer exist, having been eroded away completely, or that the thin organic rich lenses observed are patchily variable in terms of content and thickness.